Electromagnetic shielding of appliances or assemblies is becoming increasingly important for development of electrical appliances with a high layer density and very high operating frequencies, owing to the increase associated with this in electromagnetic interference fields within and outside the electrical appliances.
Shielding housings or shielding walls are generally provided for electromagnetic shielding. However, in general, openings for cables to pass through are required in such shielding housings or shielding walls, and these adversely affect the shielding effect. In general, relatively large openings have to be provided so that it is also possible to pass through a cable plug, which is large in comparison to the cable diameter, together with a cable. The larger the opening, the greater the extent to which the shielding effect is also reduced, however. With circular openings, the reduction in the shielding effect is governed essentially by their diameter, while with rectangular openings, it is governed essentially by their diagonals. This thus results in the problem of designing such an opening firstly to be sufficiently large for cable plugs to be passed through with ease while, on the other hand, to be sufficiently small to maintain an adequate shielding effect.
In practice, openings which are originally designed to be large are frequently subsequently reduced in size by covers which have to be fitted after a cable has been passed through. However, this involves additional material costs and assembly effort.